1. Field of the Invention
This invention relates to apparatus and methods for forming corrugations in metal heat exchange tubing.
2. Brief Description of the Prior Art
Finned heat exchange tubing is well known in the art for use in radiators, heat exchangers, refrigeration condensors, etc. Many types of apparatus and methods are known for the application of heat exchange fins to heat exchanger tubing.
It is also well known to form heat exchange fins integrally from the wall of heat exchange tubing members. It is also known to corrugate heat exchange tubing into longitudinally extending or circumferentially or helically extending corrugations to provide an increased surface area for heat exchange somewhat equivalent to the the application of external fins to the tubing. The production of helical corrugations and tubing, however, has in the past required the use of an internal mandrel and an external corrugating die cooperable therewith to form the desired corrugations. Such equipment has limited the length of helically corrugated tubing to the length of the mandrel used in the corrugating operation. The has not been a practical method for continuous corrugating of indefinite length of thin walled heat exchange tubing.
Benson U.S. Pat. No. 2,954,121 discloses apparatus for extrusion of metal tubing with helical fins formed intergrally thereon.
Slade U.S. Pat. No. 3,008,187 discloses an extrusion die for extruding thermoplastics having helical corrugations for orienting the plastic material in different directions.
Atkin U.S. Pat. No. 3,267,712 discloses extrusion die for extruding tubing with longitudinally extending fins thereon.
Brothers U.S. Pat. No. 4,159,739 discloses a method and apparatus for forming heat exchange fins integrally from the material of heat exchange tubing.
Ford U.S. Pat. No. 3,850,227 discloses a helically corrugated heat exchange tubing and makes reference in his specification to other types of tubing and to apparatus used for forming such tubing.
Regner U.S. Pat. No. 3,988,804 discloses the use of a rotating die having helical internal fins for forming thin walled tubular cellophane film into a pleated or shirred form having helically formed pleats.